SWG Flow Sensor vs Water Sensor & Flow Rate Issues

[JohnT]

Split off of this topic. Jason Lion

Lack of eyeballs in the returns is most likely your problem. A little back-pressure will keep the cell full of water at lower flow rates.

 

[mas985]

Re: Air/gas in SWG with pump on low speed

I don't think smaller eyeballs would help. In fact, they may make things worse. The problem is that there is not enough flow rate to purge the gas out of the cell. Reducing the size of the eyeballs will only reduce the flow rate further so it would probably may the situation worse.

A picture of your SWG setup might help but just looking at the manual, probably the only solution is to run at higher RPM. The cell design lends itself to this type of problem. The axial cells will do better at purging the gas. Although they tell you not to, plumbing it upside down might help.

Also, does the SWG have a bypass?

 

[OzPool]

Re: Air/gas in SWG with pump on low speed

Thanks, I have written to Astral Pools (manufacturer of pump and chlorinator) as shown below. I'll let you know the response.

I am hoping that you can assist me with a problem I am having with my Astral chlorinator and pump.

I purchased a VX9T chlorinator around 12 months ago and it was installed as per the installation instructions. It has been operating well since installation.

In the interests of reducing my energy bill, I recently purchased a Viron EVO P320 pump. I decided on this pump because I figured there would be no compatibility issues with my VX9T chlorinator. I understand that there is a warranty condition with this pump that requires installation by a trained installer, so the pump was installed by Pool and Spa Warehouse.

I was excited when I placed my energy meter on the pump and saw just how efficiently it can run, but this excitement soon turned to concern when I realised that at low speed there was not sufficient flow through the chlorinator to clear all the bubbles of hydrogen gas. The bubbles gradually form into one large bubble, which eventually exposes the cell. I have since played around with varying the speed and reducing the output of the chlorinator, but without success. For example, with the pump on low speed (even if I increase it to 1500rpm) and the chlorinator set on the lowest setting (1/8) a bubble slowly forms to the point that the cell is exposed. Even on medium speed, with the chlorinator running at 3/8 or above, the gas bubble forms.

I’ve outlaid $1050 on the EVO pump with the expectation that the purchase would pay itself off in a short space of time by reducing my energy bill. As I seem unable to run the pump at low speed and medium speed it seems I have completely wasted my money.

It appears to me that the design of the VX9T cell housing lends itself to the accumulation of gas bubbles when running a low speed pump. I notice that all Astral chlorinators use the same cell housing. Is there anything that can be modified to address this problem? For example, is it possible to install the chlorinator upside down or on its side to allow an escape path for the gas bubbles, but still be covered by the cell warranty?

Your assistance in resolving this matter would be very much appreciated.

 

[Strannik]

Re: Air/gas in SWG with pump on low speed

you wouldn't want to plumb your cell upside down if Hurlcon doesn't have a separate flow switch

if the pump fails/gets turned off, the cell will still have water in it, so the unit will not detect lack of water flow and continue working
the water will boil out and housing will melt.

 

[mas985]

Re: Air/gas in SWG with pump on low speed

Most flow switches detect flow not water so even if it is upside down, it will still detect no flow.

Detecting just water would not work either way so it is unlikely that they do that. The cell could be installed upright and still be full of water without flow.

 

[JohnT]

Re: Air/gas in SWG with pump on low speed

I don't think smaller eyeballs would help. In fact, they may make things worse. The problem is that there is not enough flow rate to purge the gas out of the cell. Reducing the size of the eyeballs will only reduce the flow rate further so it would probably may the situation worse.

A picture of your SWG setup might help but just looking at the manual, probably the only solution is to run at higher RPM. The cell design lends itself to this type of problem. The axial cells will do better at purging the gas. Although they tell you not to, plumbing it upside down might help.

Also, does the SWG have a bypass?

I'm going to stick to my guns and say I think eyeballs will help. The OP says his returns have none right now, and I suspect that rather than being a gas build-up issue that it is too little resistance to flow for the pump to fill the plumbing on the pressure side of the pump. I'll gladly partake of crow sandwich if they don't help. It will not be my first. :-D

 

[mas985]

Re: Air/gas in SWG with pump on low speed

When priming as system (i.e. removing air), it isn't pressure which removes the air, it is the flow rate of the water. The more turbulent the flow (i.e. higher flow), the easier it is to remove the air. This is the same principle behind a priming pump and why a clogged impeller or even a dirty filter makes it harder to prime. Same with solar.

Reducing the size of the eyeballs will increase pressure and reduce flow rate. It is the flow rate that removes the air and not the pressure.

 

[OzPool]

Re: Air/gas in SWG with pump on low speed

Hi guys and thanks for the healthy debate on my problem. I should clarify the original topic title by removing the word "Air". With the salt cell turned off the cell housing stays fully primed and no bubbles appear in the unit at all. In fact, the SWG stays fully primed at all times because it is around 1 metre (that's 3 feet guys ) below the water level. The bubbles that are forming in the cell are an accumulation of the gas that comes from the electrolysis process.

I still plan to try eyeballs in an attempt to improve skimming, but for this particular problem I reckon if anything they would make the situation worse.

 

[Strannik]

Re: Air/gas in SWG with pump on low speed

Most flow switches detect flow not water so even if it is upside down, it will still detect no flow.

Detecting just water would not work either way so it is unlikely that they do that. The cell could be installed upright and still be full of water without flow.

the flow switches do, the flow sensors don't
a lot of SWGs have sensors, not switches and by the looks on a picture that model is one of them

if the cell is installed upright the water will drain, unless of course it's some fancy installation with cell being very close to the ground and all the other piping being well above it

 

[OzPool]

Re: Air/gas in SWG with pump on low speed

if the cell is installed upright the water will drain, unless of course it's some fancy installation with cell being very close to the ground and all the other piping being well above it

As per above, the cell is always full as it is below water level

 

[OzPool]

Re: Air/gas in SWG with pump on low speed

i'd check the SWG manual for the minimal flow rate and ensure that you get at least that

I would do that too, if only the manual included such information.

Back to one of my original questions - is there anything in the sand filter that I should check? The SWG seems to get adequate flow when the multi-port is set to re-circulate.

 

[mas985]

Re: Air/gas in SWG with pump on low speed

the flow switches do, the flow sensors don't
a lot of SWGs have sensors, not switches and by the looks on a picture that model is one of them

if the cell is installed upright the water will drain, unless of course it's some fancy installation with cell being very close to the ground and all the other piping being well above it

Sorry I disagree. Some plumbing systems do not drain when the pump is shut off. Only if you have a VRV for solar can air get into a plumbing system. Otherwise, the plumbing will remain full of water since there is no other entry point for the air. Also, any plumbing system that is below water level would not have air in the pipes even with a VRV.

A flow sensor that only detects the presence of water would not work since some plumbing setups do not drain of water when shut off so I serious doubt they would use a water detection system. For safety reasons, All flow sensors must detect flow not just water. If they don't, they are disaster waiting to happen.

From the Hurlcon VX9T SWG manual:

Your VX Chlorinator incorporates a run dry safety cut out. When the Chlorinator turns the filter pump on, it will check for water flow. If no water flow is detected within 3 minutes, the chlorinator will turn the pump off. This is designed to protect the pump seal and parts from overheating if no water flow is present.

Also

Apart from messages displayed on the User display, there are two warning indicators.
(a) LOW SALT: This indicates that the concentration of salt has reduced within you pool. To rectify, add salt
at approx. 50kg per 50000 litres of water (see 3.5 Salt level below)
(b) NO FLOW: This indicates that the Chlorinator thinks that there is no flow to the cells. Potential
problems/solutions are described in the Diagnostics section.

 

[mas985]

Re: Air/gas in SWG with pump on low speed

OzPool,

One thing to try is to turn on the waterfall (i.e. both returns and waterfall set on with the handle up) and see if that gives you some extra flow rate that will purge the cell. I am assuming that the valve that is off in the picture is for the waterfall.

 

[OzPool]

Re: Air/gas in SWG with pump on low speed

Thanks Mas, you're assumption is correct and I can give it a try. I can't really use the waterfall in its currrent state (that's another project - see signature), but the plumbing uses a heavy duty flexible hose so I can just re-route that back into the pool for the time being. I'll give it a go and report back.

 

[Strannik]

Re: Air/gas in SWG with pump on low speed

Sorry I disagree. Some plumbing systems do not drain when the pump is shut off. Only if you have a VRV for solar can air get into a plumbing system. Otherwise, the plumbing will remain full of water since there is no other entry point for the air. Also, any plumbing system that is below water level would not have air in the pipes even with a VRV.

A flow sensor that only detects the presence of water would not work since some plumbing setups do not drain of water when shut off so I serious doubt they would use a water detection system. For safety reasons, All flow sensors must detect flow not just water. If they don't, they are disaster waiting to happen.

And yet a lot of systems have the sensors, rather than switches. The 'disaster' is mitigated by installation instructions. Hence why it's not recommended to install them turned around.

With regards to the air not being in the system - your cell generates plenty of gas. In one scenario the gas will all go up into the piping, accumulating at the top, but when the cell is installed correctly it will quickly push down all the water and expose the sensors.

From the Hurlcon VX9T SWG manual:

Your VX Chlorinator incorporates a run dry safety cut out. When the Chlorinator turns the filter pump on, it will check for water flow. If no water flow is detected within 3 minutes, the chlorinator will turn the pump off. This is designed to protect the pump seal and parts from overheating if no water flow is present.

Also

[quote:1nbo4gqg]Apart from messages displayed on the User display, there are two warning indicators.
(a) LOW SALT: This indicates that the concentration of salt has reduced within you pool. To rectify, add salt
at approx. 50kg per 50000 litres of water (see 3.5 Salt level below)
(b) NO FLOW: This indicates that the Chlorinator thinks that there is no flow to the cells. Potential
problems/solutions are described in the Diagnostics section.

[/quote:1nbo4gqg]

that's just the wording in the user manual, it's not a technical specification. devil is always in implementation details

By the way, here is the quote from the same manual, just several pages down:

4.1 Cell Maintenance
Your VX Chlorinator has an automatic cleaning feature that under normal conditions, will keep the
cell plates clear of deposits of salt and calcium.
VX Series cells have a negative charge sensor that monitors the flow and salt levels of the water.
This sensor is designed to be fail safe. As it is negative charges deposits of calcium or other
debris may be deposited on it and cause it to indicate a low salt or no flow condition. Should a
low salt condition be indicated, have your salt level checked at your local pool shop. If the low
salt condition persists, or a no flow condition is indicated when the supply pump is operating, you
may need to manually clean your chlorinator Cell.

I rest my case

 

[mas985]

Re: Air/gas in SWG with pump on low speed

4.1 Cell Maintenance
Your VX Chlorinator has an automatic cleaning feature that under normal conditions, will keep the
cell plates clear of deposits of salt and calcium.
VX Series cells have a negative charge sensor that monitors the flow and salt levels of the water.
This sensor is designed to be fail safe. As it is negative charges deposits of calcium or other
debris may be deposited on it and cause it to indicate a low salt or no flow condition.[/b] Should a
low salt condition be indicated, have your salt level checked at your local pool shop. If the low
salt condition persists, or a no flow condition is indicated when the supply pump is operating, you
may need to manually clean your chlorinator Cell.

I think you just proved my point.

Also, I think you are confusing a water sensor with a flow sensor. It's not a water sensor, it is a FLOW sensor. It senses the movement of water. A SWG MUST detect water flow/movement and not just the presence of water. Otherwise gas can build up in the cell. Switch or sensor doesn't matter.

 

[Strannik]

Re: Air/gas in SWG with pump on low speed

4.1 Cell Maintenance
Your VX Chlorinator has an automatic cleaning feature that under normal conditions, will keep the
cell plates clear of deposits of salt and calcium.
VX Series cells have a negative charge sensor that monitors the flow and salt levels of the water.
This sensor is designed to be fail safe. As it is negative charges deposits of calcium or other
debris may be deposited on it and cause it to indicate a low salt or no flow condition.[/b] Should a
low salt condition be indicated, have your salt level checked at your local pool shop. If the low
salt condition persists, or a no flow condition is indicated when the supply pump is operating, you
may need to manually clean your chlorinator Cell.

I think you just proved my point.

Also, I think you are confusing a water sensor with a flow sensor. It's not a water sensor, it is a FLOW sensor. It senses the movement of water. A SWG MUST detect water flow/movement and not just the presence of water. Otherwise gas can build up in the cell. Switch or sensor doesn't matter.

it's a negative charge sensor. it merely detects a presence of water, not whether it flows or not. The gas will only build up until the sensor is exposed.

Trust me, I worked in a company that manufactures them and have seen various different models on the bench.
You can put the cell in the bucket, and it will work. It's not a flow detector.
OzPool, sorry we seem to have hijacked your thread

 

[mas985]

Re: Air/gas in SWG with pump on low speed

OzPool,

I am sorry that you think we are hijacking your thread but my concern is mostly for your safety. If what Strannik is saying is true, then I would not use that SWG because to me it is a safety hazard. In the documentation it claims that the "VX Series cells have a negative charge sensor that monitors the flow" but if it only detects the presence of water, then it isn't really monitoring flow at all and hydrogen (and in some cases oxygen) gas can easily build up in the cell. Of course that is happening anyway with the low speed operation. I really don't understand why this manufacture would be so negligent in their design. It is a lawsuit waiting to happen. I just sent an email to the manufacture for confirmation but if true, I would demand a refund and use a different SWG.

But another way to confirm this type of operation (question to OzPool); Does the cell shut off after gas starts to accumulate in the cell when running on low speed? If not, then the sensor flow or water, is not working properly or they were incredibly stupid and put the sensor at the bottom of the cell instead of top where the gas accumulates. At a minimum, the cell should shut off with only a tiny bit of gas to minimize the risk.

 

[Strannik]

Re: Air/gas in SWG with pump on low speed

it's not a safety hazard, it's very reliable if the unit is installed in accordance with installation instructions
there are millions of units with such sensors out there, i'm yet to hear about the problem with one.

if anything, these sensors are more susceptible to false 'no water' alarms when the cell gets dirty. as opposed to flow switches, where the wires can short or the switch can get jammed closed.

a simple way to confirm would be as i said, put the cell in a bucket of water so that the sensor is covered and see if it will generate chlorine.

 

[mas985]

Re: Air/gas in SWG with pump on low speed

Now to the topic of the post. When running the pump at lower speeds, not all the bubbles are being flushed out of the SWG and a larger bubble is forming in the top of the cell housing.

That indicates to me that the sensor is NOT shutting off the cell which I consider to be a safety hazard. How much gas can accumulate before the unit shuts off?